Cosmogenic 10Be Chronology of Late Pleistocene Cirque Glaciation in Ireland and its Paleoclimatic Implications

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This proposal will reconstruct glacier fluctuations in Ireland and their relation to past climate change. The team will integrate data and modeling of the late Pleistocene glacial history of Ireland and its relation to climate change based on new, internally consistent, high-precision 10Be ages that constrain the age of cirque glacier moraines from sites that provide broad coverage of Ireland. Well-dated records of fluctuations of these former cirque glaciers will provide important paleoclimate information because of their short response times (~10-100 years) to climate change. Moreover, cirque glaciers provide limiting constraints on the vertical and spatial extent of the Irish Ice Sheet that otherwise remains largely unconstrained in the western, southern and eastern sectors where several cirque-bearing uplands occur. The broadly distributed study sites are located to provide constraints on regional variability in equilibrium line altitudes that can be evaluated with climate-glacier models and provide important insights into the factors controlling the ice sheet. After collecting and interpreting the limiting ages of Irish glacial moraines, the team will use results from the transient simulation of the last deglaciation run with the National Center for Atmospheric Research Community Climate System Model v3 coupled atmospheric-ocean General Circulation Model, and from their own set of simulations at 3,000 year intervals starting at 21,000 years. In order to resolve important regional climatic forcing (e.g. topographically induced circulations), the team will conduct high-resolution (5 to 15 km) climate simulations over Ireland with boundary conditions provided by the General Circulation Model runs. The team will then use output from the regional model to simulate the mass balance of reconstructed cirque glaciers by incorporating an energy balance model that they have calibrated and tested at South Cascade Glacier, WA and Collier Glacier, OR.This proposal includes letters of support from NCAR/CGD for CCSM3 model use and interpretation, and from the Purdue PRIME Lab for beryllium-10 measurements on 81 samples, and will provide support for a graduate student to be trained in the collection and preparation of samples, as well as the model runs and their interpretation.